Police have recovered some of the 5,000 bags of sugar suspected to contain mercury that were stolen from the Bollore godown in Changamwe, Mombasa County, last week.
Officers in Jomvu Sub-county confiscated the sugar from a house in Bangladesh slum, also in Changamwe.
They surrounded the house in the operation that began on Saturday morning.
The officers arrested the owner of the house, a woman, for questioning, on suspicion that she was among those who broke into the godown.
A senior detective who requested anonymity said, "The Bangladesh community helped us recover the goods."
He urged patience until officers from the Directorate of Criminal Investigations finish the investigation.
Police will brief the media on the matter later on Saturday afternoon.
Last week, Changamwe Sub-county Police commander Daudi Loronyokwe said another 300 bags of "good" sugar were also stolen from the godown.
Mr Loronyokwe said seven people were arrested in connection to the theft of the 300 bags.
"The watchman who had been guarding the mercury sugar escaped but we are looking for him," he said.
The theft is said to have taken place in the last three weeks and is believed to have been an inside job, according to Mr Loronyokwe.